/*
 * Copyright (c) 2022. YuzukiTsuru <GloomyGhost@GloomyGhost.com>.
 * lessampler is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License v3.0 as published by
 *  the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * You should have received a copy of the GNU Lesser General Public License v3.0
 * along with lessampler. If not, see <http://www.gnu.org/licenses/>.
    ============
    SHA-1 in C++
    ============
    Original C Code
        -- Steve Reid <steve@edmweb.com>
    Small changes to fit into bglibs
        -- Bruce Guenter <bruce@untroubled.org>
    Translation to simpler C++ Code
        -- Volker Diels-Grabsch <v@njh.eu>
    Safety fixes
        -- Eugene Hopkinson <slowriot at voxelstorm dot com>
    Header-only library
        -- Zlatko Michailov <zlatko@michailov.org>
    lessampler inline
        -- YuzukiTsuru <gloomyghost@gloomyghost.com>
*/

//
// Created by gloom on 2022/7/15.
//

#include "SHA1.h"

namespace {
    void reset(uint32_t digest[], std::string &buffer, uint64_t &transforms) {
        /* SHA1 initialization constants */
        digest[0] = 0x67452301;
        digest[1] = 0xefcdab89;
        digest[2] = 0x98badcfe;
        digest[3] = 0x10325476;
        digest[4] = 0xc3d2e1f0;

        /* Reset counters */
        buffer = "";
        transforms = 0;
    }

    uint32_t rol(const uint32_t value, const size_t bits) {
        return (value << bits) | (value >> (32 - bits));
    }


    uint32_t blk(const uint32_t block[16], const size_t i) {
        return rol(block[(i + 13) & 15] ^ block[(i + 8) & 15] ^ block[(i + 2) & 15] ^ block[i], 1);
    }


    /*
     * (R0+R1), R2, R3, R4 are the different operations used in SHA1
     */
    void R0(const uint32_t block[16], const uint32_t v, uint32_t &w, const uint32_t x, const uint32_t y, uint32_t &z, const size_t i) {
        z += ((w & (x ^ y)) ^ y) + block[i] + 0x5a827999 + rol(v, 5);
        w = rol(w, 30);
    }


    void R1(uint32_t block[16], const uint32_t v, uint32_t &w, const uint32_t x, const uint32_t y, uint32_t &z, const size_t i) {
        block[i] = blk(block, i);
        z += ((w & (x ^ y)) ^ y) + block[i] + 0x5a827999 + rol(v, 5);
        w = rol(w, 30);
    }


    void R2(uint32_t block[16], const uint32_t v, uint32_t &w, const uint32_t x, const uint32_t y, uint32_t &z, const size_t i) {
        block[i] = blk(block, i);
        z += (w ^ x ^ y) + block[i] + 0x6ed9eba1 + rol(v, 5);
        w = rol(w, 30);
    }


    void R3(uint32_t block[16], const uint32_t v, uint32_t &w, const uint32_t x, const uint32_t y, uint32_t &z, const size_t i) {
        block[i] = blk(block, i);
        z += (((w | x) & y) | (w & x)) + block[i] + 0x8f1bbcdc + rol(v, 5);
        w = rol(w, 30);
    }


    void R4(uint32_t block[16], const uint32_t v, uint32_t &w, const uint32_t x, const uint32_t y, uint32_t &z, const size_t i) {
        block[i] = blk(block, i);
        z += (w ^ x ^ y) + block[i] + 0xca62c1d6 + rol(v, 5);
        w = rol(w, 30);
    }

/*
 * Hash a single 512-bit block. This is the core of the algorithm.
 */
    void transform(uint32_t digest[], uint32_t block[16], uint64_t &transforms) {
        /* Copy digest[] to working vars */
        uint32_t a = digest[0];
        uint32_t b = digest[1];
        uint32_t c = digest[2];
        uint32_t d = digest[3];
        uint32_t e = digest[4];

        /* 4 rounds of 20 operations each. Loop unrolled. */
        R0(block, a, b, c, d, e, 0);
        R0(block, e, a, b, c, d, 1);
        R0(block, d, e, a, b, c, 2);
        R0(block, c, d, e, a, b, 3);
        R0(block, b, c, d, e, a, 4);
        R0(block, a, b, c, d, e, 5);
        R0(block, e, a, b, c, d, 6);
        R0(block, d, e, a, b, c, 7);
        R0(block, c, d, e, a, b, 8);
        R0(block, b, c, d, e, a, 9);
        R0(block, a, b, c, d, e, 10);
        R0(block, e, a, b, c, d, 11);
        R0(block, d, e, a, b, c, 12);
        R0(block, c, d, e, a, b, 13);
        R0(block, b, c, d, e, a, 14);
        R0(block, a, b, c, d, e, 15);
        R1(block, e, a, b, c, d, 0);
        R1(block, d, e, a, b, c, 1);
        R1(block, c, d, e, a, b, 2);
        R1(block, b, c, d, e, a, 3);
        R2(block, a, b, c, d, e, 4);
        R2(block, e, a, b, c, d, 5);
        R2(block, d, e, a, b, c, 6);
        R2(block, c, d, e, a, b, 7);
        R2(block, b, c, d, e, a, 8);
        R2(block, a, b, c, d, e, 9);
        R2(block, e, a, b, c, d, 10);
        R2(block, d, e, a, b, c, 11);
        R2(block, c, d, e, a, b, 12);
        R2(block, b, c, d, e, a, 13);
        R2(block, a, b, c, d, e, 14);
        R2(block, e, a, b, c, d, 15);
        R2(block, d, e, a, b, c, 0);
        R2(block, c, d, e, a, b, 1);
        R2(block, b, c, d, e, a, 2);
        R2(block, a, b, c, d, e, 3);
        R2(block, e, a, b, c, d, 4);
        R2(block, d, e, a, b, c, 5);
        R2(block, c, d, e, a, b, 6);
        R2(block, b, c, d, e, a, 7);
        R3(block, a, b, c, d, e, 8);
        R3(block, e, a, b, c, d, 9);
        R3(block, d, e, a, b, c, 10);
        R3(block, c, d, e, a, b, 11);
        R3(block, b, c, d, e, a, 12);
        R3(block, a, b, c, d, e, 13);
        R3(block, e, a, b, c, d, 14);
        R3(block, d, e, a, b, c, 15);
        R3(block, c, d, e, a, b, 0);
        R3(block, b, c, d, e, a, 1);
        R3(block, a, b, c, d, e, 2);
        R3(block, e, a, b, c, d, 3);
        R3(block, d, e, a, b, c, 4);
        R3(block, c, d, e, a, b, 5);
        R3(block, b, c, d, e, a, 6);
        R3(block, a, b, c, d, e, 7);
        R3(block, e, a, b, c, d, 8);
        R3(block, d, e, a, b, c, 9);
        R3(block, c, d, e, a, b, 10);
        R3(block, b, c, d, e, a, 11);
        R4(block, a, b, c, d, e, 12);
        R4(block, e, a, b, c, d, 13);
        R4(block, d, e, a, b, c, 14);
        R4(block, c, d, e, a, b, 15);
        R4(block, b, c, d, e, a, 0);
        R4(block, a, b, c, d, e, 1);
        R4(block, e, a, b, c, d, 2);
        R4(block, d, e, a, b, c, 3);
        R4(block, c, d, e, a, b, 4);
        R4(block, b, c, d, e, a, 5);
        R4(block, a, b, c, d, e, 6);
        R4(block, e, a, b, c, d, 7);
        R4(block, d, e, a, b, c, 8);
        R4(block, c, d, e, a, b, 9);
        R4(block, b, c, d, e, a, 10);
        R4(block, a, b, c, d, e, 11);
        R4(block, e, a, b, c, d, 12);
        R4(block, d, e, a, b, c, 13);
        R4(block, c, d, e, a, b, 14);
        R4(block, b, c, d, e, a, 15);

        /* Add the working vars back into digest[] */
        digest[0] += a;
        digest[1] += b;
        digest[2] += c;
        digest[3] += d;
        digest[4] += e;

        /* Count the number of transformations */
        transforms++;
    }


    void buffer_to_block(const std::string &buffer, uint32_t block[16]) {
        /* Convert the std::string (byte buffer) to a uint32_t array (MSB) */
        for (size_t i = 0; i < 16; i++) {
            block[i] = (buffer[4 * i + 3] & 0xff)
                       | (buffer[4 * i + 2] & 0xff) << 8
                       | (buffer[4 * i + 1] & 0xff) << 16
                       | (buffer[4 * i + 0] & 0xff) << 24;
        }
    }
}


SHA1::SHA1() {
    reset(digest, buffer, transforms);
}

void SHA1::update(const std::string &s) {
    std::istringstream is(s);
    update(is);
}

void SHA1::update(std::istream &is) {
    while (true) {
        char sbuf[64];
        is.read(sbuf, 64 - std::size(buffer));
        buffer.append(sbuf, static_cast<std::size_t>(is.gcount()));
        if (buffer.size() != 64) {
            return;
        }
        uint32_t block[16];
        buffer_to_block(buffer, block);
        transform(digest, block, transforms);
        buffer.clear();
    }
}

/*
 * Add padding and return the message digest.
 */
std::string SHA1::final() {
    /* Total number of hashed bits */
    uint64_t total_bits = (transforms * 64 + buffer.size()) * 8;

    /* Padding */
    buffer += (char) 0x80;
    size_t orig_size = buffer.size();
    while (buffer.size() < 64) {
        buffer += (char) 0x00;
    }

    uint32_t block[16];
    buffer_to_block(buffer, block);

    if (orig_size > 64 - 8) {
        transform(digest, block, transforms);
        for (size_t i = 0; i < 16 - 2; i++) {
            block[i] = 0;
        }
    }

    /* Append total_bits, split this uint64_t into two uint32_t */
    block[16 - 1] = (uint32_t) total_bits;
    block[16 - 2] = (uint32_t) (total_bits >> 32);
    transform(digest, block, transforms);

    /* Hex std::string */
    std::ostringstream result;
    for (unsigned int i: digest) {
        result << std::hex << std::setfill('0') << std::setw(8);
        result << i;
    }

    /* Reset for next run */
    reset(digest, buffer, transforms);

    return result.str();
}

[[maybe_unused]] std::string SHA1::from_file(const std::string &filename) {
    std::ifstream stream(filename.c_str(), std::ios::binary);
    SHA1 checksum;
    checksum.update(stream);
    return checksum.final();
}